title: Angiotensin II stimulates phosphorylation of nuclear lamins via a protein kinase C-dependent mechanism in cultured vascular smooth muscle cells.
abstract: Angiotensin II (ang II) induces c-fos gene expression in part via a protein kinase C-dependent mechanism in cultured vascular smooth muscle cells (VSMC). However, little is known about the mechanisms by which protein kinase C regulates nuclear functions. We examined the ability of ang II to phosphorylate nuclear lamina proteins in VSMC and the possibility that protein kinase C is involved in these putative phosphorylation events. Ang II stimulated the phosphorylation of Triton X-100- and high salt-insoluble nuclear envelope proteins with molecular weights of 70,000, 67,000, and 60,000. These proteins were identified as lamins A, B, and C, respectively, based on their mobilities on two-dimensional gel electrophoresis and interaction with antibodies to lamins as detected by immunoblot analyses. After a 2-min delay, phosphorylation levels of lamins increased, peaked at 20-30 min, and were sustained for at least 60 min after ang II stimulation. The threshold, half-maximal, and maximal concentrations of ang II which induced phosphorylation of lamins were 0.1, 0.5-1, and 100 nM, respectively. Phorbol 12-myristate 13-acetate also induced these reactions, whereas ionomycin did not. Down-regulation of protein kinase C by prolonged treatment with phorbol 12,13-dibutyrate attenuated ang II-induced phosphorylation of lamins. In vitro phosphorylation of nuclear envelope proteins by protein kinase C revealed that lamins served as substrates for this enzyme. These results indicate that ang II induces phosphorylation of lamins in cultured VSMC and suggest that protein kinase C is either directly or indirectly involved in these reactions. The results raise the possibility that phosphorylation of nuclear proteins is one of the important steps by which the protein kinase C signaling pathway regulates agonist-induced nuclear events.
authors.affiliation: Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322.
authors.forename: T
authors.initials: T
authors.lastname: Tsuda
authors.forename: R W
authors.initials: RW
authors.lastname: Alexander
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D015536:Down-Regulation; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009685:Nuclear Envelope / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats
chemical_list: D000804:Angiotensin II; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C